In the first few months of life babies have erratic sleep patterns. They learn through experience that they should be more active in daytime and sleep longer through the night. Babies have to sort through the incredible amount of stimulation that they are exposed to on a daily basis. They go from the quiet dim light of mothers womb into a world of noise, light and changing textures and levels of motion. This can be quite hard to sort through and some become overstimulated making it difficult for them to settle and resulting in prolonged crying and difficulty settling.
Fussy babies are often fussy because they have not had sufficient sleep and are overwhelmed by the experiences of the day. Prolonged sleep disturbance only exacerbates these problems. This is why naps are important. A babies nap is the first opportunity for them to learn to self settle. While night sleep is important for both mother and baby daytime naps are little top ups which help baby come to terms with all the stimulation of the environment.
As they grow and age the naps become fewer and night sleep increases but, if your child is "fussy" do not remove the opportunity for naps and think that by doing so you will gain a better night sleep. Naps are just as important to a growing child.